Cirolana merlion, Sidabalok & Bruce, 2018

Sidabalok, Conni M. & Bruce, Niel L., 2018, Review of the Cirolana ‘ pleonastica-group’ (Crustacea: Isopoda: Cirolanidae) with description of four new species from the Indo- Malaysian region, Raffles Bulletin of Zoology 66, pp. 177-207 : 180-186

Cirolana merlion , new species

( Figs. 1–4 )

Material examined. All Singapore. Holotype: male (7.2 mm) ( ZRC 2018.0199 ), between St John’s Island and Lazarus Island, 01°13.043′N, 103°51.319′E, OTC0103 OTR356, trap 22.4 m, coll. H. Wong and party, 3 April 2014.

Paratypes. 3 males (6 [dissected], 6.5, 7.6 mm), 1 ♀ (8.5 mm) ( ZRC 2018.0200 ), St John’s Island , 1°13.020′N, 103°51.122′E, SW119 SS4934, trap, coll. N.L. Bruce, 30 May 2013 ; 8 males (5.3, 5.3, 5.4, 5.5, 5.6, 5.7, 6.1, 6.8 mm), 11 females (4.8, 4.9, 5.0, 5.0, 5.0, 5.0, 5.0, 5.9, 5.9, 6.0, 6.6 mm) ( ZRC 2018.0201 ), same data as holotype ; 5 males (7, 7.4, 7.5, 9.0, 10.0 mm), 9 females (6.9, 7.0, 7.5, 8.0, 8.0, 8.0, 8.3, 9.0, 9.0 mm) ( ZRC 2018.0202 ), St John’s Island–Lazarus Island , 01°12.958′N, 103°51.316′E, SS4941 SW138, trap 13.5 m, coll. N.L. Bruce and party, 31 May 2013 ; 4 females (9.0, 9.5, 10.0, 11.0 mm) ( ZRC 2018.0203 ), St John’s Island–Lazarus Island , 01°12.958′N, 103°51.316′E, SS4940 SW137, trap 25 m, coll. N.L. Bruce and party, 31 May 2013 ; 4 males (6.8, 8.0, 8.5, 8.8 mm), 48 females (not measured) ( ZRC 2018.0204 ), St John’s Island– Lazarus Island , 01°12.958′N, 103°51.316′E, SW147, trap 45 m, coll. N.L. Bruce, 1 June 2013 ; 3 males (6.2, 6.4, 6.8 mm) ( MTQ W34883), same data as previous ; 2 males (4.3, 8.0 mm), 15 females (5.2–9.0 mm, average 6.8 mm) ( ZRC 2018.0205 ), St John’s Island–Lazarus Island , 01°12.958′N, 103°51.316′E, SS4942 SW 137, trap 25 m, coll. N.L. Bruce and party, 31 May 2013 .

Description. Body ( Fig. 1A ) 2.9 times as long as greatest width, dorsal surfaces punctate, widest at pereonite 5, lateral margins subparallel. Rostral point absent. Eyes ( Fig. 1F ) separated by about 82% width of head, eye colour black. Pereonite 1 and coxae 2–3 ( Fig. 1B ) each with posteroventral angle rounded; coxae 5–7 with entire oblique carina; posterior margins of pereonites 6–7 with irregular submarginal nodules. Pleon ( Fig. 1I ) with pleonite 1 not visible in dorsal view; pleonites 3–5 posterior margin with regular nodules; posterolateral angles of pleonite 2 forming acute point, extending posteriorly to anterior of pleonite 3; pleonite 3 with 1 median tubercle (the largest) and 5 sublateral tubercles on each side, posterolateral margins not extending to posterior margin of pleonite 5, acute; pleonite 4 with 1 median tubercle and 2 sublateral tubercles on each side, posterolateral margin of pleonite 4 rounded, clearly extending beyond posterior margin of pleonite 5; pleonite 5 with 1 median tubercle and 3 sublateral tubercles on each side and posterolateral angles overlapped by lateral margins of pleonite 4. Pleotelson ( Fig. 1J ) 0.7 times as long as anterior width; with 2 submedian tubercle rows on dorsal surface (4 tubercles each); lateral margins straight, margins smooth, posterior margin truncate, without median point, with 8 robust setae.

Antennula ( Fig. 1D ) peduncle articles 1 and 2 entirely fused; articles 3 and 4 0.7 times as long as combined lengths of articles 1 and 2, article 3 1.3 times as long as wide; flagellum with 10 articles, extending to anterior of pereonite 1. Antenna ( Fig. 1C ) peduncle article 4 1.8 times as long as wide, 1.6 times as long as article 3, and 4 short simple setae (distal); article 5 as long as article 4, 1.9 times as long as wide, anterodistal angle with cluster of 2 short simple setae; flagellum with 21 articles, extending to posterior of pereonite 4.

Frontal lamina ( Fig. 1E ) pentagonal, 1.5 longer than greatest width, lateral margins anteriorly concave, diverging slightly towards anterior, anterior margin concave and acute, forming median point.

Mandible ( Fig. 2D ) molar process anterior margin with 16 flat teeth; with proximal cluster of long simple setae; right mandible spine row composed of 9 spines; palp article 2 with 10 distolateral setae, palp article 3 with 2 robust biserrate and 13 plumose setae. Maxillule ( Fig. 2B ) mesial lobe with 3 large and circumplumose RS; lateral lobe with 11 RS. Maxilla ( Fig. 2C ) lateral lobe with 4 long simple setae; middle lobe with 11 long simple setae; mesial lobe with 8 distal simple setae, with 6 proximal simple and plumose setae. Maxilliped ( Fig. 2A ) palp article 2 mesial margin with 5 slender setae, lateral margin distally with 1 slender setae; article 3 mesial margin with 14 slender setae, lateral margin with 7 slender setae; article 4 mesial margin with 9 slender setae, lateral margin with 4 slender setae; article 5 distal margin 10 setae, lateral margin with 7 setae; endite with 2 long CPS, and 2 coupling setae.

Pereopod 1 ( Fig. 3A ) basis 2.2 times as long as greatest width, superior distal angle without cluster of acute setae, inferior distal angle with cluster of 3 acute setae; ischium 0.6 times as long as basis, inferior margin with 2 setae, inferior distal margin with 2 RS, superior distal margin with 2 RS; merus inferior margin with 6 molariform RS, set as 2 and 4, with 3 simple setae, inferior distal margin with 1 RS, superior distal angle with 2 RS; carpus inferior margin with 1 RS and 1 simple setae; propodus 2.0 times as long as wide, inferior margin with 2 RS, inferior distal margin with 1 large RS and 3 simple setae, superior distal with 2 simple setae; dactylus 0.8 as long as propodus. Pereopod 2 ( Fig. 3B ) ischium inferior margin with 2 long acute RS, inferior distal margin with 2 RS, superior distal margin with 1 long acute seta and 1 plumose seta; merus inferior margin with 4 stout RS and 1 RS, set as single row, inferior distal margin with 1 stout RS and 2 RS, superior distal margin with 2 long acute RS and 2 plumose setae; carpus inferior distal margin with 3 acute RS; propodus 2.5 as long as wide, with 2 clusters of acute RS, inferior margin with 2 RS, inferior distal margin with 1 large RS and 2 simple setae; dactylus 0.8 as long as propodus. Pereopod 3 similar to pereopod 2. Pereopod 6 ( Fig. 3C ) similar to pereopod 7. Pereopod 7 ( Fig. 3D ) basis 2.3 times as long as greatest width, superior margin weakly convex, inferior margin with 4 palmate setae; ischium 0.5 as long as basis, inferior margin with 3 RS (set in group of 2 and 1), inferior distal angle with 3 RS, superior distal angle with 4 RS (2 biserrate); merus 0.9 as long as ischium, 1.6 times as long as wide, inferior margin with 3 RS, superior distal angle with 7 RS (2 biserrate), inferior distal angle with 6 RS; carpus as long as ischium, 2 times as long as wide, inferior margin with 2 RS, superior distal angle with 12 RS (10 biserrate), inferior distal angle with 11 RS (5 biserrate); propodus as long as ischium, 4.3 times as long as wide, inferior margin with 2 clusters of RS (set as 1 and 1), superior distal angle with 1 slender seta, 1 plumose seta and 2 RS, inferior distal angle with 2 RS; dactylus 0.5 as long as propodus.

Penes ( Fig. 1G ) opening flush, penial openings separated by 5.7% of sternal width.

Pleopod 1 ( Fig. 4A ) exopod 1.4 times as long as wide, lateral margin straight, distally narrowly rounded, medial margin weakly oblique, mesial margin strongly convex, with PMS from distal one-third, with ~30 PMS; endopod 2.1 times as long as wide, distally narrowly rounded, lateral proximal margin convex, with PMS on distal margin only, mesial margin with PMS one third of mesial margin, endopod with ~13 PMS; peduncle 0.7 times as wide as long. Pleopod 2 ( Fig. 4B ) exopod with ~41 PMS, endopod with ~13 PMS; appendix masculina with parallel margins, 0.9 times as long as endopod, distally narrowly rounded. Pleopod 3 ( Fig. 4C ) exopod with ~43 PMS, endopod with ~12 PMS. Pleopod 4 ( Fig. 4D ) exopod with ~41 PMS, endopod with ~10 PMS. Pleopod 5 ( Fig. 4E ) exopod with ~40 PMS. Pleopods 2–5 peduncle distolateral margin with prominent acute RS, 3–5 endopods with distomesial serrate scales.

Uropod ( Fig. 1H ) peduncle ventrolateral margin with 2 RS, lateral margin with 1 medial short acute RS, posterior lobe about as long as endopod; rami extending beyond pleotelson, marginal setae in single tier, apices not bifid. Endopod apically not bifid; lateral margin weakly convex and proximally straight, proximal lateral margin without RS; distal lateral margin with 2 RS, mesial margin weakly convex, with 7 RS. Exopod not extending to end of endopod, 2.5 times as long as greatest width, apically not bifid, medial process sub-acute and prominent; lateral margin weakly convex, with 5 visible widely separated RS; mesial margin convex, with 4 RS.

Female. Similar to the male.

Size. Males 4.3–10.0 mm, mean 6.8 mm (n=26); nonovigerous females 5.0–11.0 mm, mean 7.1 mm (n=38); all from type series.

Variation. RS count was measured from 82 specimens of type series. Uropod exopod lateral: 4 = 15.8%, 5 = 79.3%, 6 = 4.9%; mesial: 2 = 11%, 3 = 87.8%, 4 = 1.2%. Uropod endopod lateral: 2 = 91.5%, 3 = 8.5%; mesial: 6 = 13.4%, 7 = 26.8%, 8 = 52.5%, 9 = 7.3%. Pleotelson: 6 = 8.5%, 7 = 15.9%, 8 = 75.6%.

Remarks. Cirolana merlion , new species, is characterised by the frontal lamina having concave lateral margins, two transverse impressed lines on pereonites 5–7, three prominent median tubercles on pleonites 4 and 5, two transverse distinct impressed carinae on the lateral margin of pleonite 4 and two submedian longitudinal rows of tubercles on the pleotelson; the exopod of uropod has 5 robust setae on the lateral margin (vs. 3 on most species of the group).

Species similar to C. merlion are C. oreonota Bruce, 1986 , C. kombona Bruce, 1986 , and C. capricornica Bruce, 1986 all with antennula peduncle articles 1 and 2 fused (with distinct suture) and the pattern of nodules on pleonites 3–5 and on pleotelson (several sublateral nodules with one median tubercle). The last three species differ in having a broader frontal lamina with straight lateral margins (vs. slender and concave) and smaller size lateral nodules on pleonites 3–5, and four (vs. five) robust setae on the exopod of uropod. Furthermore, Cirolana oreonota also differs in having a more rounded uropodal endopod mesial margin and more rounded lateral margin of uropodal exopod. Cirolana kombona has two transverse impressed lines on pereonites 2–3 (vs. 1) and three on pereonites 4–7 (vs. 1–2) and a straight lateral margin of endopod of pleopod 1 (vs. lateral proximal margin convex). Cirolana capricornica has the frontal lamina with straight lateral margins, absence of submarginal nodules on posterior margin of pereonite 6, the presence of submarginal nodules only at the edges of posterior margin of pereonite 7, smaller median tubercles on pleonites 4–5 and on pleotelson, pleotelson lateral margins sinuate, posteriorly narrowly rounded (not truncate).

Distribution. Known only from Singapore; intertidal to 45 metres.

Etymology. Named after a famous Singapore landmark, the Merlion (noun in apposition).

Figures

Fig. 1. Cirolana merlion n. sp. A, B, E–G, I, holotype male (7.2 mm) (ZRC 2018.0199), Singapore. C–D, H, J, paratype male (6.0 mm) (ZRC 2018.0200), Singapore. A, dorsal view; B, lateral view; C, antennal peduncle; D, antennula; E, frons; F, head; G, penial openings; H, uropod; I, pleon; J, pleotelson.

Fig. 2. Cirolana merlion n. sp. A–D, paratype male (6.0 mm) (ZRC 2018.0200), Singapore. A, maxilliped; B, maxillule; C, maxilla; D, right mandible.

Fig. 3. Cirolana merlion n. sp. A–D, paratype male (6.0 mm) (ZRC 2018.0200), Singapore. A, pereopod 1; B, pereopod 2; C, pereopod 6; D, pereopod 7.

Fig. 4. Cirolana merlion n. sp. A–E, paratype male (6.0 mm) (ZRC 2018.0200), Singapore. A, pleopod 1; B, pleopod 2; C, pleopod 3; D, pleopod 4; E, pleopod 5.